It is known that although metallic containers, such as those obtained for example by aluminium injection casting technology, maintain their functional nature for different types of heat transmission and are particularly suitable for electric, gas or glass ceramic cookers where the heat for the container is produced respectively through direct contact with an electric resistance, with the flame produced by gas combustion or via a special glass ceramic surface, they are not suitable for induction cookers where the heat for the utensil is produced by taking advantage of the phenomenon of magnetic induction, where a magnetic field of variable intensity heats ferric materials that are within its reach.
Therefore it is necessary to either manufacture the whole utensil in a ferromagnetic material with the disadvantages and limitations this involves (cost, weight and handling, heat resistance and durability, etc.), or attach to the bottom wall of the utensil, at least one plate of ferromagnetic material capable of absorbing an efficient yield of calorific energy produced by electromagnetic induction because the so-called losses through hysteresis are transformed into calorific energy.
Different solutions are known in the art, which aim at integrating a ferromagnetic plate underneath the bottom wall of a cooking container made from a different material, for example, an austenitic steel or aluminium.
In this sense the following patents can be quoted. Patent ES-A-2002980 proposes a cooking container on the bottom wall of which an intermediate heat diffusing metal plate is attached and underneath said plate a ferromagnetic stainless steel lining, with the elements being welded together. Patent ES-A-2108284 describes a culinary utensil with a heat conducting bottom wall having a perforated metallic sheet attached to the outer face of said bottom wall during casting, using the flow of metal to fill said perforations. Patent ES-A-2135632 proposes a cooking utensil with a metallic plate or strip that has openings which receive filler parts made from a ferromagnetic material, the ensemble being joined together by a weld bead applied with a laser beam to the bottom wall of a container made from austenitic steel. Patent application DE-A-3713660 describes a cooking utensil made from cast-moulded aluminium, preferably a saucepan, that includes at least one solid metallic part attached to the outer part of its bottom wall in the cast-moulding process with the aluminium. Patent application EP-A-722688 describes a culinary utensil with a part attached by a high temperature pressure to the outer face of its bottom wall. Patent application WO-A-97/09136 describes a method for manufacturing a piece of metal intended to constitute the bottom wall of a cooking utensil, obtained by roll forging, plastically deforming the metal, and in which manufacturing process, one variant thereof envisages the inclusion of some metal parts that can be induction heated integrated with the metal part in the forging process.